1. Field of the Invention
This invention relates to a wheeled conveyance system, and more particularly to a manually or power driven wheelchair and transmission system for a wheelchair.
2. Description of the Prior Art
Numerous types of wheelchair systems exist. Such systems, however, generally do not take good advantage of the musculature of the human body. The wheelchairs are customarily designed without the capability to readily match the system to the strength or stature of the particular operator or to differing uses.
The most common systems utilize two large hand driven wheels. A problem with such systems, particularly when used outside, is that the operator's hands and arms are in contact with or close to the driving wheels, which wheels are in contact with the ground. This creates an unclean environment about the operator's arms and hands. Use of the wheels also tends to callous the hands of the operator, and requires frictional restraint by the hands for braking. And, such systems place stresses on the operator's arms and hands which result in physical problems such as, for example, carpal tunnel syndrome.
Manually powered wheel chair systems require use of upper body musculature, and typically require use of the operator's arms positioned to the side of the body. This positioning relies heavily on the operator's triceps, and does not take good advantage of additional upper body and arm characteristics. For example, the biceps of the human body are typically more powerful than the triceps. Biceps are more useful when pulling, and triceps are more useful when pushing.
Additionally, the pectoral muscles provide strength, particularly when used together with the biceps. Pectoral muscles, however, do not provide as much aid to the triceps. In most present wheel chair systems the operator pushes forwardly on the upper portion of the wheels, inputting power, but the operator does not input energy on the return of the hands and arms to position for the next push stroke. There are systems marketed by Rock N'Roll Inc. of Texas wherein forward and rearward motion of handlebars on bicycle type structures is inputted as power to a specially configured gear system.
Additionally, present systems are designed for a broad cross section of users, without consideration of the musculature strength of an operator or the modification of that strength over time, for example, as a young operator grows.
It is therefore desirable to provide a manually powered wheel chair system, and a transmission for wheelchairs, which improves upon these and other limitations. It is also desirable to provide such systems which are compatible with power mechanisms.